34th America's Cup: multihulls!

The comments that Oracle's guys should learn from the A Class sailors, and that they should have handled the foils differently, are pretty amusing.

Spithill finished 5th at the last A nationals, behind multiple Olympic cat medallist and world champ Bundy, ahead of Olympic cat medallist and world champ Anderson and Olympic cat medallist Landenberger (I've forgotten whether Landy won a T worlds as well). Tom also scored a win in that event, ahead of Gashby, Stalky, etc as well as finishing 7th on foils in a Moth worlds.

Of course, none of these guys hold a candle to their critics in terms of sailing skill, experience or knowledge, but they do have some idea about foils and fast cats.

 

Not picky at all. Only picky, if you wish to over inflate a simple known definition into something it is not.

When people talk about their boats and conditions they were/are in etc..the comments become more and more like a fisherman's tail....to the point of becoming "legendary".!!

Thus if one really wishes to to be "grown" up when talking about such events, at least use "grown" up definitions and not cloud the minds of others with subjective feelings/thoughts. It is what leads to pointless arguments and my dog is bigger than yours.

Otherwise, why not say the boat was in a typhoon...it is a still wind event, or is that being picky?

Thus to say the gust was over 30knots....you must have been there and measured the wind speed...yes? If not, one can only generalise and generalise about the nature of a gust. Otherwise there is a lot of wool being pulled over the eyes of those that are less informed about such matters, why let facts get in the way, eh?...all for the sake of a "good story"

To say it was gusting is fine...but to add an absolute in order to make it sound "better"...

 

Jeeez again Ad Hoc, (repeat of my first sentence) and ... fisherman's tail, eh?

 

They have pulled the Oracle AC72 back out of the water. The platform does not look too bad all things considered.

http://www.sail-world.com/Australia/Americas-Cup:-Images-of--Oracles-AC72-being-hauled-from-the-water/102977

 

CT249, If you're referring to my comments, please understand that I wasn't saying what they should have done to save it, I was merely explaining to Stephen Ditmore that releasing the mainsheet at the moment the bows were already down would have just assisted the pitchpole as the wing loads up with extra power, and sheeting it in would be the only way to stall the wing & depower it. The guys on board have many multihull hours under them and they knew this as well, which is why they tried to carry on bearing away while holding the main IN. I was not inferring that they responded incorrectly, merely explaining to others here who might think in monohull terms how to remedy a situation, which doesn't always work on multi's.
My thought that they should not have attempted the bearaway without coming up to full speed first, and if the boat was designed with no reserve bouyancy in the bows and designed to rely on the foils to provide the lift absent in the bows, still stands, and is confirmed by their own designers who's comments on the matter are listed a few posts ago. In no way was I inferring that these guys should learn from the world's top cat sailors - They ARE the world's top cat sailors.

 

Found it here courtesy of Doug :
"As team engineer Dirk Kramers explains, their AC 72 is supposed to be
foiling when they bear away. "Our hull is quite small, much smaller than
Team New Zealand's, so we are reliant on the foils to keep it from
pitchpoling in a bearaway," explained Kramers. "

The pic Doug posted to show it was foiling before the incident happened proves the opposite - it was climbing out of the water so fast with a bow up attitude, that the next manouvre could only be a return to earth in bow down attitude. This proves that this boat in no way has stable foiling sorted.

 

I should have made it clear that I wasn't thinking of releasing the mainsheet to change the angle of the whole wing (shrouds would prevent it weathercocking nose-to-wind), but of releasing the camber by releasing the flaps on the back of the wing-sail. And now that I've realized which side the wind is coming from in the video your initial recommendation that they needed to power up and get the windward hull out of the water makes sense. So as I understand it you're saying they should have initially powered up to get the windward hull up, then if that was unsuccessful and the bows stuffed they should have deliberately stalled the wing?

 

Do these together drive the point home?

 

Hi Stephen,
I think this is exactly what Gary Baigent and I have been trying to say..

It looks like TNZ designed a compromise boat that, if foiling doesn't work, the hull design can still do the job, while OR17 have put all their eggs in the foiling basket, without enough reserve bouyancy in the bows. So in rough conditions if the boat is leaping out of the water and not foiling, TNZ could opt to put in non-foiling boards for the day, while it looks like OR don't have that option available.

I think Mr. Spithill is looking forward to boat #2, and they are probably having long meetings in the design office.

 

34th AC on Foils

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Stephen, as best I can tell,l both hulls were flying at the time the windward hull went bow down followed by the lee hull and a pitchpole.

 

34th AC on Foils!

I disagree about the hull design being faulty and a "cause" of the pitchpole.
I think the pitchpole was caused by a failure in the foiling system and/or a failure to have a backup emergency plan. This could be anything from a broken linkage to failure of the foil controller("pilot") to a combination of breakdowns. The foils are extraordinarily powerful and can send the boat into the air* like the picture I posted previously. The fact that they pitchpoled points directly to a failure of the foiling system, not of the hull design, in my opinion.
* again below

 

Is that photo immediately prior to the pitchpole under discussion? Wasn't the boat on port tack in the video?

 

34th AC on foils

=======================
No, I just used it to illustrate the power of the foils-in this case the lee foil.

 

34th AC on Foils!

Check this audio out-it backs up my theory(actually my eyes!) that they were foiling at the time of the pitchpole:
http://www.kqed.org/news/story/2012...rewmember_recalls_capsizing?category=bay area

 

My post was partly referring to your post and partly to others - Doug's comment that he doesn't "think the crew was ready to handle the boat in those conditions", Petereng's reference to operator error and the fact that it seemed that they "just gave it a go to see what happens?", Gary's comment that the Oracle guys were "asking for it" and that people should ask the A Class guys about it. As you say,there were bloody good cat sailors on board, of course they know about this stuff!

As earlier noted, I agree that sheeting in is a common depowering technique; more common in some types of craft than in others simply because the dynamics of CoE/CLR and apparent wind work differently, at a guess. But there is info that indicates that sheeting in would not have helped in this case.

Steve Clark doesn't seem to believe that "sheeting it in would be the only way to stall the wing & depower it". On SA he wrote;

"On staying sheeted in on a bearaway:
It's not a sail, it has a slot and maintains lift at a higher angle of attack.
So if you stay sheeted on, it doesn't turn off (lee stall) as quickly as a sail.It also has a higher Coefficient of Lift, so as you try to power down through the zone, you also have to deal with more power than a sail generates.
It's different."

He posted again later with l/d graphs and noted "Note that the power goes up faster, goes up further and stays on longer.
All good reasons for having a wing on a racing sailboat, and good reason not to stay sheeted on hard during a bear away.

So rather than being some lack of knowledge that stopped them from sheeting in, it appears that practice and theory shows that sheeting in to depower does not apply in the same way to solid wings.

The comment that these guys are the world's best appears to be at odds with the comment that you "thought that they should not have attempted the bearaway without coming up to full speed first." You are saying that the world's best did something that you think they "should not have attempted".

When there is a difference of opinion between the world's best who were on the boat and those of us who are not the world's best and were not on the boat, surely logic demands that we should assume that they know best.

This is not saying that we cannot criticise, but we should have a pretty damn good factual basis for any criticism and the fact that we would not have done it that way on soft-sailed 16 footer lowrider cats does not mean that they should not have done it that way on a solid-wing 72 foot foiling cat.